Add the Nessa subdomain landing page served at nessa.freno.me/.
- index.tsx: hero, feature highlights, CTA band, and footer themed via
useSite() brandColor and useDarkMode(); deliberately avoids freno.me
web-auth UI (Nessa uses Clerk) and uses a non-fabricated 'Coming soon'
CTA since there's no app-store presence yet.
- meta.ts: deterministic PageHeadProps (title, description, OG) as a pure
module mirroring the page-head-meta testability pattern; feature copy is
derived from real nessaCommunityRouter capabilities (clubs, challenges,
social.feed, events).
- meta.test.ts: resolves metadata over SITE_CONFIG.nessa + pathname '/' to
assert title suffix composition, canonical, OG image fallback, and
description content.
